Modern social welfare and social welfare institutions have undergone three distinct periods of historical development. In the early and mid-nineteenth century, in North America and in western and central Europe, reformers tinkered with a variety of social insurance schemes, mainly pensions for the aged and certain voluntary or market-based remedies. They also organized various institutions designed to care for the mentally ill, promote public health, ward off epidemics, expand public education, and improve the lot of entrepreneurs, artisans, mechanics, and the poor. These programs influenced only fractions of any nation's population. This was an age of liberal and democratic idealism, and these efforts reflected the spirit of that age. Between the 1870s and the 1920s, in the second period, the United States, together with Great Britain, Imperial Germany, Sweden, Denmark, Austria, and France, had various social insurance schemes that embraced some groups in their polities, thus reflecting commonly embraced notions of efficiency and hierarchy. The third phase began with the Great Depression of the 1930s, especially with the United States and its broad Social Security program and with most of western and central Europe, which adopted something like an all-embracing social welfare state in the wake of World War II (1939–1945). In the 1990s and early 2000s opponents in Europe and the United States made some politically effective criticisms of the welfare state, thus suggesting that yet another phase of modern social welfare's history may be about to begin, or even that the social welfare experiment may be terminated